Hydrological Modeling-Based Assessment of the Impact of Urbanization on Runoff From Watercourse Catchments

Urban expansion significantly alters natural hydrological regimes and increases the risk of flooding, particularly in suburban catchments undergoing rapid land-use transformation. The replacement of permeable surfaces with impervious infrastructure reduces infiltration and increases pressure on existing drainage systems. This study evaluates the hydraulic performance of a suburban catchment in southwestern Poland (18.78 km²) using an integrated modelling approach combining SWMM hydrodynamic simulations with high-resolution (1 m) terrain analysis in SCALGO Live Poland. Results show that an imperviousness level of approximately 18% is sufficient to exceed the hydraulic capacity of the drainage system during design rainfall events. The introduction of two retention reservoirs (total capacity 180 000 m³) reduced peak flows by 32% and eliminated 93% of high-risk flood zones. The study highlights the importance of integrated hydrological modelling for planning effective stormwater retention strategies in rapidly urbanizing catchments.